This invention relates to the problem of preparing support materials useful as components of olefin polymerization catalysts, and the process used to prepare them. In particular, it relates to the preparation of insoluble catalyst support materials containing magnesium, halide and hydrocarbyloxide in well defined ratios. Most particularly, this invention concerns the preparation of substantially pure solid halomagnesium hydrocarbyloxide catalyst support materials with well defined and uniform composition.
The term "hydrocarbyloxide" is intended to cover structures of the formula --OR where R is "hydrocarbyl", i.e., a moiety formed by the removal of hydrogen from a hydrocarbon, e.g. alkyl, aryl and alkylaryl. There are many examples in the prior art of olefin polymerization catalysts obtained by combining a component comprising magnesium halide and a titanium halide with an activating organoaluminum compound. The polymerization activity, stereospecificity, and comonomer incorporation characteristics of such compounds may be manipulated in various ways. In some cases this is accomplished by controlling the particular composition of the magnesium halide, for instance, by including some alkoxy ligands in the magnesium halide compound, or by halogenating a particular magnesium dialkoxide to prepare the magnesium halide. Magnesium halide-supported catalysts for the polymerization of olefins prepared by halogenating a magnesium alkoxide are described in U.S. Pat. Nos. 4,400,302 and 4,414,132 to Goodall, et. al., for example. Since the morphology of the polymer is generally controlled by that of the catalyst, much effort has been expended in attempting to control the morphology of such catalysts.
Examples of catalyst components that are prepared in processes employing materials containing magnesium, halide and hydrocarbyloxide can be found in European Patent Publication No. 301,894. This patent document illustrates the preparation of catalyst components with specific useful polymerization characteristics (co-monomer incorporation, polymer crystallinity, etc.) by employing these materials.
In view of the above considerations, the nature of the magnesium-containing component of a polymerization catalyst composition, and the process used to prepare it are very important. The prior art includes many strategies for the preparation of magnesium, halide and hydrocarbyloxide containing polymerization catalyst support materials. Most of these strategies are based on the work of Turova and Turevskaya (Journal of Organometallic Chemistry, vol. 42, (1972), pp 9-17). Turova et al. suggested thermolysis of Mg(OR).sub.2 and MgX.sub.2 mixtures (X=halogen; R, R'=alkyl, aryl, etc), eq. (1), or the alcoholysis of Grignard reagents, eq. (2): ##STR1## Subsequent work has varied from this earlier work in certain details, such as in U.S. Pat. Nos. 4,814,313 to Murata et. al. and 4,220,554 to Scata et. al. where Grignard reagents were formed in situ and then reacted with alkoxy ligand sources, eq. (3). ##STR2## Another minor variation can be found in U.S. Pat. No. 4,820,879 to Mehta, who uses HX (eq. (4)) as the halogen ligand source, rather than MgX.sub.2 as in eq. (1). EQU Mg(OR).sub.2 +HX.fwdarw.XMgOR+HOR (4)
In the method of eq. (3), halide is present before the hydrocarbyloxide is formed, and may or may not be present in the desired ratio to magnesium because of the Schlenk equilibrium. In the method of eq. (4), the halogen ligand source must react with only part of the hydrocarbyloxy ligands present, in order to get the desired product stoichiometry, and the extent of reaction is difficult to control.
Common concerns in the preparation of insoluble solid materials are the issues of uniformity, purity, and composition. Catalyst support materials are substances that may be categorized as either "ionic structures" or "covalent infinite arrays". In these cases it is not always a simple matter to establish the uniformity and purity of a material. Although the above strategies (eq. (1) through eq. (4)) purport to prepare solid compounds such as "XMgOR", they are not supported by examples where the chemical and spectroscopic characterization of the product demonstrates that it is a uniform solid of well defined composition with established purity. (Terminology taken from Advanced Inorganic Chemistry, 5th edition, by F. A. Cotton, and G. Wilkinson: John Wiley and Sons; New York, 1988). In many cases it is possible, and even likely, that the product was actually a mixture, e.g. of MgX.sub.2 and Mg(OR).sub.2, that merely had the correct average composition. In all cases where there was spectroscopic characterization sufficient to differentiate between a solid of uniform composition and purity, and a mixture (e.g. U.S. Pat. Nos. 4,820,879 and 4,792,640 to Mehta), mixtures were found.